A spectroscopic apparatus has been used as a core mechanism in various industrial fields such as optical fields, chemical fields, and marine engineering fields. The spectroscopic apparatus measures intensities of a variety of wavelengths generated from an object and represents the measurement information in the form of a graph or a spectrum. A degree at which the spectroscopic apparatus accurately and finely represents the information of the object is called “resolution”. The resolution is an important factor to evaluate the performance of a spectroscope.
Among spectroscopic apparatuses, a miniature spectroscopic apparatus, which employs a filter device to reduce the manufacturing cost, can be conveniently used for a portable purpose. The filter device can be intensively produced by densely arranging filters.
A filter device technology employing nano-processes is used to micro-miniaturize the spectroscopic apparatus in size and to significantly save the production price of the spectroscopic apparatus in mass-production resulting from the micro-miniaturization. The miniature spectroscopic apparatus produced through such a process greatly helps to measure the characteristics of a material in an industrial site outside a laboratory. In addition, the spectroscopic apparatus can be easily connected with a computer or other electronic devices and used together. In addition, the spectroscopic apparatus based on a filter device can measure the spectrum information of a light source within a short period of time.
The limitation of the resolution that can be reached by the spectroscopic apparatus may be determined depending on the number of filters provided in the optical filter device. Accordingly, in order to enhance the resolution, the increase in the number of the filters may be taken into consideration. However, it may be actually difficult to increase the number of the filters provided in the optical filter device due to a physical restriction condition and spectrum distortion.
There may be a transmittance function of an optical filter as another factor to determine the resolution. Actually, since the transmittance function of the optical filter is non-ideal in a low-cost nano-process filter device, the non-ideal optical filter distorts original spectrum information of an optical signal. Accordingly, in order to find the original spectrum information of the optical signal, it is necessary to perform digital signal processing with respect to spectral components of an input signal.
As representative digital signal processing schemes, there has been introduced non-patent document 1, J. Oliver, W. B. Lee, S. J. Park, H. N. Lee, “improving resolution of miniature spectrometers by exploiting sparse nature of signals,” Opt. Exp. 20, 2613-2625 (2012)), and patent document 1, Korean Patent Application No. 10-2012-0079171. The patent document 1 is filed for the invention invented by an inventor of the present invention and provides an L1 norm minimization algorithm realized to find original spectrum information of an optical signal. However, the technologies provided in the above documents have a limitation in enhancing the resolution. Accordingly, the increase in the number of filters provided in the optical filter device must be inevitably taken into consideration.